The present invention generally relates to an image analyzing apparatus for analyzing an image by radiating a target object to be analyzed such as living tissues or organs and, more particularly, to an apparatus for the fluorometric analysis.
As is well known to those skilled in the art, the oxidation-reduction (oxidoreduction) of pyridine-nucleotide present in the living tissue or organ such as NADH (reduced nicotinamide adenine dinucleotide) and NADPH (reduced nicotinamide adenine dinucleotide phosphate), which pyridine-nucleotide is hereinafter referred to as "PN", provides an indication of the state of respiratory function (metabolism) of the living tissue. The reduced PN has a property of emitting fluorescence when excited by ultraviolet radiation. Therefore, by analyzing the oxidoreduction of the PN through the fluorometric technique, the state of respiratory metabolism of the living tissue can be monitored. Moreover, if the fluorescence emission from the PN is analyzed in two-dimensional geometry, the affected locality of the living tissue at which abnormal respiratory metabolism takes place can be located.
However, it has been found that, during the clinical examination of the PN fluorescence image, the presence of blood in the living tissue being examined provides an optical interference to the fluorescence emission. In other words, since the blood shows an absorption band within a spectrum of wavelengths of the fluorescence emission from the PN, the intervention of the blood brings an undesirable optical interference on the PN fluorescence emission with the consequence that the more fluorescence emission tends to be indicated when the blood content is small at a given locality of the living tissue than when it is great at the same locality. Therefore, the optical interference brought about by the intervention of the blood must be compensated for in order to avoid such a false indication.
In view of the foregoing, the assignee of the present invention has disclosed, by way of the Japanese Patent Publication No. 55-46726, published Nov. 26, 1980, a method for the compensation for the optical interference to the PN fluorescence emission resulting from fluctuations in blood content in the living tissue. According to this publication, the application of the compensating method to determine the accurate fluorescence emission from the PN in the living tissue requires the use of an interference equation descriptive of the optical interference, which equation was derived from the relationship between the fluorescence emission, resulting from the radiation of exciting light, and the amount of reference light radiated onto and then reflected from the living tissue.
In establishing the interference equation according to the above mentioned publication, however, the prior art method requires the use of a living tissue different from the living tissue of interest. This means that not only can the interference equation so derived be not regarded as applicable universally to all living tissues, but also the interference equation so derived requires adjustment depending on the optical conditions. Therefore, it has been found that the clinical use of the interference equation descriptive of the interference brings about no practical result.